An image system, such as a camera, can include an optical lens, an image sensor (e.g., a complementary metal-oxide-semiconductor (“CMOS”) or charged coupled device (“CCD”) sensor), and other digital processing circuitry. In some cases, an image sensor of the image system can include a color filter array (“CFA”), which can enable the image sensor to capture color signals. For example, different types of coating on the CFA may allow the CFA to pass a selective narrow band of light while blocking other portions of the visible light spectrum. The color filtering provided by the CFA thereby limits the wide sensitivity of the image sensor to the visible light spectrum.
For each type of image system, a spectral curve of the CFA can be defined. In addition, the color response of the image sensor can be characterized. Following the characterization, the image system can perform additional digital processing. In some cases, the digital processing performed by the image system can include an optimization process for designing a color correction matrix (“CCM”). As a result, CCM and other color adjustment procedures in a digital processing pipeline can jointly transform an image sensor output to a final output for the user.
Typically, during the manufacturing of image sensors, a per module calibration process can be performed on red-green-blue (“RGB”) image sensors. Unfortunately, the light source that is used during the calibration process needs to have uniform brightness. Moreover, one or more special targets are also required during the calibration process. Such calibration processes can slow down manufacturing and add cost.